The present invention relates to a fuel battery.
A fuel battery generally has a stack structure in which unit cells 12 (fuel battery cells), such as the one shown in FIG. 11, are stacked (refer to Japanese Laid-Open Patent Publication No. 2011-150801). Each unit cell 12 includes two frames 13 and 14. A membrane electrode assembly (MEA) 15 is arranged in a bonded portion of the frames 13 and 14. The membrane electrode assembly 15 includes a solid polymer electrolyte membrane 16 formed by an ion-exchange membrane, an electrode catalyst layer 17 located at an anode side, and an electrode catalyst layer 18 located at a cathode side. The periphery of the solid polymer electrolyte membrane 16 is held between the frames 13 and 14.
A gas diffusion layer 19 located at the anode side is laminated on a surface of the electrode catalyst layer 17. A gas diffusion layer 20 located at the cathode side is laminated on a surface of the electrode catalyst layer 18. A first gas passage forming body 21 located at the anode side is stacked on a surface of the gas diffusion layer 19. A second gas passage forming body 22 located at the cathode side is stacked on a surface of the gas diffusion layer 20. A flat separator 23 is bonded to a surface of the first gas passage forming body 21. A flat separator 24 is bonded to a surface of the second gas passage forming body 22.
The first gas passage forming body 21 and the second gas passage forming body 22 have the same structure. Thus, the structure of the second gas passage forming body 22 will be described below. In FIGS. 11 and 12, the same reference numerals as the second gas passage forming body 22 are given to those components of the first gas passage forming body 21 having the same structure.
The second gas passage forming body 22 includes a flat plate material 25. A number of locations of the flat plate material 25 are cut and raised to form first projections 26a and second projections 26b. The first projections 26a and the second projections 26b, which form gas passages, are cut and raised to project toward the gas diffusion layer 20.
The second projections 26b are arranged in rows. A first projection 26a is located adjacent to a gap between two second projections 26b located next to each other in the same row. The first projections 26a and the second projections 26b contact the gas diffusion layer 20. This forms main passages h1, which serve as oxidant gas passages, between the flat plate material 25 and the gas diffusion layer 20. Adjacent ones of the main passages hl are in communication with each other through sub-passages h2 located between the first projections 26a and the second projections 26b. 
The flat plate material 25 includes small third projections 27 projecting toward the separator 24. The third projections 27 are located at an upstream side with respect to the gas flow direction P in correspondence with the first and second projections 26a and 26b. As shown in FIGS. 11 and 12, the third projections 27, which form water passages 28, are extruded to project toward the separator 24. The third projections 27 each contact the separator 24. This forms the water passages 28 between the flat plate material 25 and the separator 24. The depth of the water passages 28 is set within a range of, for example, 10 to 50 nm.
Each of the first projections 26a and the second projections 26b includes a communication hole 29 extending through the first or second projection 26a, 26b in a direction Q orthogonal to the gas flow direction P. That is, the first projections 26a and the second projections 26b each open at two locations, left and right sides as viewed from the gas flow direction P, to form the communication holes 29. The gas passages are in communication with the water passages 28 through the communication holes 29. The water passages 28 serve as a water guide layer.
As described above, the first gas passage forming body 21 has the same structure as the second gas passage forming body 22. However, the direction in which fuel gas flows in the gas passages formed by the first gas passage forming body 21 differs by 90 degrees from the direction in which oxidant gas flows in the gas passages formed by the second gas passage forming body 22. That is, the two directions are orthogonal.
In such a conventional fuel battery cell that has the above structure, when power is generated, that is, when the fuel gas (hydrogen) and the oxidant gas (oxygen) are respectively supplied to the anode side and the cathode side, electrochemical reaction of hydrogen and oxygen generates water in the electrode catalyst layer 18 and gas diffusion layer 20 located at the cathode side. To improve the efficiency of power generation, the fuel gas and the oxidant gas are each humidified by a humidifier and then supplied to the unit cell 12.
The water generated at the cathode side enters the gas diffusion layer 20 and the main passages h1 of the gas passage forming body 22 located at the cathode side. Some of the water generated at the cathode side is reversely diffused (permeated) through the membrane electrode assembly 15 to enter, as osmosis water, the gas diffusion layer 19 and the main passages h1 of the gas passage forming body 21 located at the anode side.
In the gas passages at the anode and cathode sides, the generated water and the osmosis water are discharged to the main passages h1 in this manner. Some of the water moves through the communication holes 29 to the water passages 28 (water guide layer) due to the capillary action of the water passages 28. The fluid pressure of gas moves the water in the water passages 28 toward the downstream side. Thus, the first gas passage forming body 21 and the second gas passage forming body 22, which are formed by porous bodies, each include a liquid-phase separation porous body passage, which is the water guide layer (water passage 28).